Dual-Pole Magnetic Attraction Downhole Magnetic Retrieval Apparatus

ABSTRACT

A magnetic retrieval tool used for collecting metallic debris and material from within a wellbore or other surrounding downhole tubular. The tool includes a tool mandrel with a removable insert which contains one or more magnets. The insert is formed such that both the north and south magnetic poles of the one or more magnets are able to attract metallic debris.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to systems and methods for cleaning the interior of tubular members. In particular aspects, the invention relates to methods and devices for removing metallic debris from tubular members using magnets. In other particular aspects, the invention relates to magnetic retrieval devices that externally present both north and south poles of magnets for removal of metallic debris.

2. Description of the Related Art

Metallic debris accumulates within wellbores and other tubular members during production of subterranean fluids, such as hydrocarbon fluids. This metallic debris typically includes tiny metal shavings and cuttings. These shavings and cuttings result from numerous frictional operations that might occur within the wellbore or tubular, including the cutting of sidetracking windows, milling, drilling through of stuck devices and objects, as well as general operations that cause metal-to-metal scraping to occur.

Devices used for the removal of metallic debris by magnets are described, for example, in U.S. Pat. No. 7,515,299, U.S. Pat. No. 7,219,724 and U.S. Pat. No. 7,137,449.

SUMMARY OF THE INVENTION

The invention provides magnetic retrieval tools for use in a wellbore or other tubular member to remove metallic debris. In preferred embodiments, a retrieval apparatus includes a tool mandrel with insert pockets. In addition, the tool mandrel preferably includes a central collar with keyed openings. The retrieval apparatus preferably includes a plurality of removable, modular inserts which reside within the insert pockets of the tool mandrel. Spacers also preferably surround the tool mandrel and help to retain the inserts in place. The tool also preferably carries stabilizers to help centralize the inserts within a surrounding tubular.

The bodies of the modular inserts each contain one or more individual magnets. The insert bodies also present an interior radial surface and an outer radial surface. The outer radial surface faces a wellbore or surrounding tubular when the insert is installed within a magnet pocket. The inner radial surface faces the tool mandrel when the insert is so installed. A removable cover may be disposed onto the interior radial surface of each insert to retain magnets within cavities within the insert body.

The inserts of the magnetic retrieval tool each preferably provide one or more longitudinal, axially extending fins which project radially outwardly from a base portion. The fins are separated from one another by recesses within which metallic debris is captured upon being attracted by the magnets within the fins of the inserts. In this embodiment, both magnetic poles of the magnetic elements within the insert body are available to attract metallic debris.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein:

FIG. 1 is a side, external view of an exemplary magnetic retrieval tool constructed in accordance with the present invention.

FIG. 2 is a side, cross-sectional view of the tool depicted in FIG. 1.

FIG. 3 is an external isometric view of the tool depicted in FIGS. 1-2.

FIG. 4 is an axial cross-sectional view taken along lines 4-4 in FIG. 2.

FIG. 5 is an isometric view of an exemplary insert used in the tool shown in FIGS. 1-4, illustrating features of the exterior radial surface of the insert.

FIG. 6 is an isometric view of the insert shown in FIG. 5, depicting features of the interior radial surface of the insert.

FIG. 7 is a further isometric view of the interior radial surface of the insert shown in FIGS. 5-6, now with an interior cover in place.

FIG. 8 is an enlarged side, cross-sectional view of portions of the tool shown in FIGS. 1-3.

FIG. 8A is an enlarged side, cross-sectional view of an alternative embodiment of a tool constructed in accordance with the present invention.

FIG. 9 is an axial cross-section taken along lines 9-9 in FIG. 2.

FIG. 10 is an external, cross-sectional view of an alternative embodiment for a tool constructed in accordance with the present invention wherein magnets are retained within longitudinal slots in inserts surrounding the central mandrel.

FIG. 11 is a side, cross-sectional view of portions of the exemplary tool shown in FIG. 10.

FIG. 12 is an external, isometric view of a radially-interior surface of an alternative exemplary insert in accordance with the present invention.

FIG. 13 is an external, isometric view of the insert shown in FIG. 12, now with magnets and retaining strips inserted.

FIG. 14 is an axial cross-section of the insert shown in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-8 and 9 illustrate a first exemplary magnetic retrieval tool 10 that is constructed in accordance with the present invention. The tool 10 includes a cylindrical tool mandrel 12 which defines a central flowbore 14 (see FIG. 2) along its length. The tool mandrel 12 is provided with threaded connections 16 at its axial ends to permit the tool 10 to be incorporated into a downhole work string.

The tool mandrel 12 presents an outer radial surface 18 with a plurality of recessed pockets 20 formed therewithin. In the depicted embodiment, there are four pockets 20. Each of the pockets 20 is preferably axially elongated and arcuately curved, as shown in FIG. 3, wherein an empty pocket 20 is shown. In the depicted embodiment, each pocket 20 is located on the opposite side of the mandrel 12 from another pocket 20. In this embodiment, the pockets 20 provide an essentially semi-circular opening. The tool mandrel 12 also presents a radially-enlarged collar 22 which projects radially outwardly from a reduced diameter portion 23 of the tool mandrel 12 and includes keyed openings 24 (see FIG. 3).

The exemplary magnetic retrieval tool 10 also includes a plurality of removable inserts 26 that reside within the pockets 20 in a complimentary manner. An exemplary insert 26 is depicted in FIGS. 5-7 apart from the other components of the tool 10. The insert 26 presents an outer radial surface 28 having a plurality of axially-oriented, outwardly-projecting fins 30 which are separated by recesses 32. One axial end of the insert 26 includes an arcuately curved engagement portion 34 (see FIG. 5). The other axial end of the insert 26 presents a plurality of keys 36 which extend axially outwardly from the main body of the insert 26. The keys 36 are shaped and sized to reside within the keyed openings 24 of the collar 22 (see FIG. 9). Those of skill in the art will understand that the keys 36 and openings 24 may be made in many different shapes so long as they are complimentary to one another.

FIGS. 6 and 7 depict the interior radial portions of the insert 26. The interior radial portion of the insert 26 is provided with a removable cover 38. The cover 38 is shown in place in FIG. 7 while FIG. 6 shows the insert 26 with the cover 38 removed. FIG. 6 illustrates that the interior radial surface 40 of the insert 26 has a plurality of magnet-retaining cavities 42 into which removable magnets 44 (see, e.g., FIG. 8) reside. As can be seen in FIG. 4, the cavities 42 and magnets 44 are each located within one of the fins 30. The exemplary magnets 44 have an elongated body having a generally rectangular cross-section. However, the magnets 44 may have other suitable cross-sectional shapes or configurations, including round, oval, triangular, or irregular. It can be appreciated that each insert 26 retains its respective multiple magnets 44 in a fixed array or matrix surrounding the mandrel 12. Further, the array of magnets 44 can be readily affixed to or removed from a surrounding relation to the mandrel 12.

Once the magnets 44 are placed within the cavities 42, the cover 38 is slid into place by disposing tapered tabs 39 on the cover 38 into grooves 41 on the insert 26. The cover 38 will retain the magnets 44 within the cavities 42 of the insert 26. In addition, the cover 38 preferably isolates the magnets 44 magnetically from the mandrel 12. It is noted that the inserts 26 themselves and covers 38 are preferably not made of magnetic material. However, the magnets 44 that are retained within the inserts 26 provide the magnetic force used to remove metallic debris from a wellbore or other tubular member. Because a non-magnetic cover 38 is disposed in between the mandrel 12 and each magnet 44, the magnets 44 are substantially isolated magnetically from the mandrel 12, thereby making the inserts 26 substantially easier to remove from the mandrel 12.

As FIG. 4 shows, the magnets 44 are located within the fins 30 of the inserts 26 when installed. The fins 20 provide a structural protective housing for the individual magnets 44. Location of the magnets 44 within the fins 30 of the inserts 26 also provides for an enlarged magnetized surface area on the outer radial surface 28 of the magnetic inserts 26. FIG. 4 illustrates that the magnets 44 present lateral north (N) and south (S) poles which provide magnetic attraction on both lateral sides 43 of the fins 30. One lateral side 43 of each fin 30 provides a first attraction surface, which uses the north magnetic poles of the magnets 44 to attract debris, while the other lateral side 43 provides a second magnetic attraction surface which uses the south magnetic pole of the magnets 44 to attract metallic debris. Metallic debris that is attracted by the magnets 44 will be captured within the recesses 32 between the fins 30. The recesses 32 provide protected chambers to prevent magnetically-attracted debris from being dislodged when the tool 10 is being removed from a surrounding wellbore or other tubular.

Preferably, the tool mandrel 12 also defines a pair exterior fluid flowpaths 46 (see FIGS. 3 and 4). If, during operation, the recesses 32 become filled with debris, fluid within a surrounding wellbore can still flow past the tool 10 via the flowpaths 46.

It is further preferred that the magnetic retrieval tool 10 includes stabilizers 47, 48 that radially surround the tool mandrel 12 and are used to centralize the magnetic bars 26 of the tool 10 within a surrounding tubular during operation. Each of the stabilizers 47, 48 are rotatable with respect to the tool mandrel 12. In a currently preferred embodiment, the stabilizers 47, 48 are formed of mating semi-cylindrical halves that are assembled around the outer circumference of the tool mandrel 12.

FIG. 8 depicts in detail one exemplary method of securing the stabilizer 47 around the tool mandrel 12. Construction of the stabilizer 48 mirrors this. Split bearing races 50 radially surround the tool mandrel 12. Roller bearings 52 are disposed between the split bearing races 50 and a surrounding split roller sleeve 54 so that the split roller sleeve 54 can rotate easily with respect to the tool mandrel 12. A stabilizer sleeve 56 radially surrounds the split roller sleeve 54 and will rotate about the tool mandrel 12 with the split roller sleeve 54.

FIG. 8 a depicts an alternative tool 10′ which has been constructed in accordance with the present invention. The tool 10′ is constructed in the same manner as the tool 10, previously described, except where indicated. In the tool 10′, there is a single bearing race 50′ disposed around the tool mandrel 12 for the stabilizer 47 a. Roller bearings 52 and ball bearings 53 are disposed between the bearing race 50′ and the surrounding stabilizer sleeve 47 a.

It is noted that in both the tool 10 in FIG. 8 and the tool 10′, shown in FIG. 8A, spacers 59 lie adjacent inserts 26 to maintain engagement between keys 36 and keyed openings 24 of collar 22. In tool 10 in FIG. 8, retaining ring 58 slides over spacers 59 and lies adjacent the roller sleeve 54. In FIG. 8A retaining ring 58 slides over spacers 59 and lies adjacent the stabilizer 47 a. The interior radial surface 60 of the retaining ring 58 contacts the engagement portion 34 of the adjacent inserts 26, thereby retaining the inserts 26 within their respective pockets 20. In order to assemble the tool 10, the keys 36 of the inserts 26 are disposed within the keyed openings 24 of the collar 22. The inserts 26 are disposed within their respective pockets 20 as this is done. Thereafter, spacers 59 are installed in pockets 20, and retaining ring 58 is slid onto each axial end of the tool mandrel 12 and in surrounding contact with the engagement portions 34 of the bars 26. Then, the stabilizers 47, 48 are installed onto the tool mandrel 12.

FIGS. 10 and 11 illustrate an alternative design for an insert 100 which could be used with the tool 10 in accordance with the present invention. The insert 100 retains a plurality of rectangular, non-magnetic magnet tubes 102. Magnets 44 are installed through the opening 108 at either end of the magnet tube 102. Magnets 44 form a fixed array or matrix surrounding the mandrel 12. Magnets 44 may be square, rectangular, round, or of other geometric shapes. In this embodiment, the inserts 100 each have a plurality of longitudinal slots 104 formed within. The slots 104 each have an internal opening 106. The slots 104 are each shaped and sized to receive one magnet tube 102. Multiple magnets 44 are disposed within magnet tube 102 in a side-by-side relation. As a result, both north and south magnetic poles of the magnets 102 are able to provide magnetic attraction on both lateral sides 43 of magnetic tube 102 and its respective fin 30. Metallic debris that is attracted by the magnets 44 will be captured within the recesses 32 between the magnet tubes 102. Once magnet tube 102 is installed in slot 104, the ends of slot 104 prevent magnets 44 from coming out of openings 108 at the end of the magnet tubes 102. Spacer 59 and retaining ring 58 retain insert 100 in recessed pockets 20 of mandrel 12.

FIGS. 12-14 depict a further alternative exemplary magnetic retrieval tool insert 110 for retaining a plurality of magnets in a fixed array or matrix about the central mandrel 12. As FIG. 12 shows, the insert 110 has a curved elongated body 112 that is shaped and sized to removably reside within a pocket, such as pocket 20 on tool mandrel 12. The body 112 presents a radial interior surface 114 within which is formed a one or more longitudinal channels 116. In the embodiment shown in FIGS. 12-14, there are three channels 116. Retaining slots 118 are also disposed within the body 112 and are located within the channels 116. The slots 118 protrude deeper into the body 112 than the channels 116 and, as illustrated in FIG. 14, largely extend into the fins 30 of the body 112.

FIGS. 13 and 14 depict the insert 110 assembled with magnets 120 (one shown in FIG. 14) and retaining strips, or members, 122. The magnets 120 are each shaped and sized to reside in a complimentary fashion within one of the slots 118. The retaining strips 122 are then disposed within the channels 116, as shown in FIGS. 13 and 14 to retain the magnets 120 within the slots 118. Preferably, an interference fit is provided between the retaining strips 122 and the channels 116. The retaining strips 122 are preferably formed of non-magnetic material and thereby serve to magnetically isolate the magnets 120 from the mandrel 12 to some degree. It is noted that retaining strips or members might be in the form of strips of rubber O-ring material, of a type known in the art.

The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention. 

1. A magnetic retrieval tool for collecting metallic material from a surrounding tubular, the tool comprising: a tool mandrel; a magnet with north and south magnetic poles disposed upon the tool mandrel; and wherein the tool presents a first outer attraction surface to attract metallic debris using the north magnetic pole of the magnet and a second outer attraction surface to attract metallic debris using the south magnetic pole of the magnet.
 2. The tool of claim 1 wherein the tool further comprises: an outer radial surface having at least one outwardly radially-projecting fin having two lateral sides; the magnet is located inside of the fin; and the first outer attraction surface is located on one lateral side and the second outer attraction surface is located on the other lateral side.
 3. The tool of claim 2 wherein the outer radial surface comprises a plurality of outwardly radially-projecting fins having two lateral sides; a magnet is disposed within each of said fins; and wherein a radially exterior recess is disposed between each two of said plurality of fins for collection of metallic debris.
 4. The tool of claim 3 wherein at least one magnet disposed within a fin comprises a non-magnetic tube containing a plurality of magnets.
 5. The tool of claim 2 further comprising: an insert disposed upon the tool mandrel, the fin being defined upon the insert; and wherein the magnet is disposed within a magnet-retaining cavity that is located at least partially within the fin.
 6. The tool of claim 5 wherein the insert is substantially formed of non-magnetic material.
 7. The tool of claim 5 further comprising a cover that is removably attached to an inner radial surface of the insert to retain the magnet within the cavity.
 8. A magnetic retrieval tool for collecting metallic material from a surrounding tubular, the tool comprising: a tool mandrel; an insert disposed upon the tool mandrel, the insert containing a magnet with north and south magnetic poles; and wherein the insert presents a first outer attraction surface to attract metallic debris using the north magnetic pole of the magnet and a second outer attraction surface to attract metallic debris using the south magnetic pole of the magnet.
 9. The tool of claim 8 wherein the insert further comprises: an outer radial surface having at least one outwardly radially-projecting fin having two lateral sides; the magnet is located inside of the fin; and the first outer attraction surface is located on one lateral side and the second outer attraction surface is located on the other lateral side.
 10. The tool of claim 9 wherein: the outer radial surface comprises a plurality of outwardly radially-projecting fins having two lateral sides; and a magnet is located inside of each fin.
 11. The tool of claim 10 wherein a radially exterior recess is disposed between each two of said plurality of fins for collection of metallic debris.
 12. The tool of claim 8 wherein the insert is substantially formed of non-magnetic material.
 13. The tool of claim 8 wherein the magnet is disposed within a magnet-retaining cavity that is located at least partially within the fin.
 14. The tool of claim 13 further comprising a cover that is removably attached to an inner radial surface of the insert to retain the magnet within the cavity.
 15. The tool of claim 8 wherein the tool mandrel includes an exterior fluid flowpath defined upon an outer radial surface to permit fluid in a surrounding tubular to flow past the tool.
 16. An insert for use with a magnetic retrieval tool, the insert comprising: an insert body that is shaped and sized to removably reside within a complimentary pocket on a tool mandrel; the insert body containing a magnet with north and south magnetic poles; and the insert body presenting a first outer attraction surface to attract metallic debris using the north magnetic pole of the magnet and a second outer attraction surface to attract metallic debris using the south magnetic pole of the magnet.
 17. The insert of claim 16 further comprising: an outer radial surface having at least one outwardly radially-projecting fin having two lateral sides; the magnet is located inside of the fin; and the first outer attraction surface is located on one lateral side and the second outer attraction surface is located on the other lateral side.
 18. The insert of claim 17 wherein the outer radial surface comprises a plurality of outwardly radially-projecting fins having two lateral sides; a magnet is disposed within each of said fins; and wherein a radially exterior recess is disposed between each two of said plurality of fins for collection of metallic debris.
 19. The insert of claim 18 wherein a radially exterior recess is disposed between each two of said plurality of fins for collection of metallic debris.
 20. The insert of claim 16 wherein the insert body is substantially formed of non-magnetic material.
 21. The insert of claim 17 wherein the magnet is disposed within a magnet-retaining cavity that is located at least partially within the fin.
 22. The insert of claim 21 further comprising a cover that is removably attached to an inner radial surface of the insert to retain the magnet within the cavity. 